Kerrostuneita

Kerrostuneita is a Finnish term used in geology to describe rocks or rock units that display distinct layers or beds produced by the accumulation of sediment over time. The underlying process, kerrostuminen, or stratification, results in a stack of beds typically visible as horizontal or gently dipping layers with variations in color, grain size, or fossil content. In sedimentary rocks such as shale, sandstone, siltstone, and limestone, the layering is a primary feature that records changes in depositional conditions.

Layers form when sediment is deposited in successive episodes of varying energy, supply, or chemistry, followed by lithification through compaction and cementation. Bedding planes separate individual layers and are often used as markers in stratigraphic correlation. Some rocks exhibit features like graded bedding, where grain size decreases upward, or cross-bedding, which records paleocurrent directions.

Kerrostuneita contrasts with a non-layered, massive rock where bedding is not preserved or is absent due to metamorphism or intense deformation. While many kerrostuneita rocks are sedimentary, metamorphic rocks can later develop foliation that is sometimes mistaken for bedding but is produced by differential rock deformation.

Understanding kerrostuneisuus aids reconstructions of past environments, sea-level changes, and sedimentary basin evolution. It also has practical relevance for natural resource exploration, as bedding planes influence porosity and fluid flow in aquifers and hydrocarbon reservoirs.